<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
	</body>
	<script type="text/javascript">
		var obj={
			a:undefined
		}
		
		console.log(obj.a);//undefined
		console.log(obj.b);//undefined
	</script>
</html>
